Condenser for a steam power plant

ABSTRACT

A method for operating a condenser, wherein the condenser is designed for condensing water vapor to form water and during operation a condensate having water accumulates in the condenser, wherein on the condensate surface a plurality of floating bodies are arranged on the condensate, wherein the floating bodies float on the condensate, wherein a large number of floating bodies are used in such a way that the condensate surface is covered, wherein the floating bodies are of spherical and/or sphere-like design, and wherein floating bodies with different sizes are used.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2015/069010 filed Aug. 19, 2015, and claims the benefitthereof. The International Application claims the benefit of EuropeanApplication No. EP14181545 filed Aug. 20, 2014. All of the applicationsare incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a method for operating a condenser.

BACKGROUND OF INVENTION

Modern power plants as a rule comprise a gas and steam turbine plant andelectric generators which are designed for generating electric energy.The torque-transmitting drive for the electric generators is carried outvia the shafts of the gas turbine and/or steam turbine.

During operation, steam, which is produced in a steam generator, flowsto a high-pressure turbine section and from there to a reheater in whichthe steam is brought up to a certain temperature. After the reheating,the steam flows to an intermediate-pressure turbine section and fromthere flows via a crossover pipe to a low-pressure turbine section.Downstream of the low-pressure turbine section, the steam flows into acondenser and condenses there to form water. In the condenser, the wateris collected to form a condensate. The condensate has a condensatesurface which in the main is fluidically connected to the flow passageof the steam turbine. Therefore, an evaporating condensate is connectedto the fact that via the fluidic connection a certain proportion ofwater vapor from the condensate flows back into the steam turbine.

The current market requirements lead to the power plant operators havingto put their power plants into more frequent, unscheduled shutdownstates of unforeseeable duration. This means, however, that after theshutting down of a steam turbine the steam which is present in the steamturbine condenses as soon as the temperature falls below the dew point.As a rule, the seal steam system is no longer in operation after such ashutdown. The combination with the water which is available from thecondenser, with the oxygen which is provided by means of the vacuumbreaker and the shaft bushing, and with the metal, leads to a possibleoccurrence of corrosion. Therefore, in the case of a stationary steamturboset the risk of stagnant-condition corrosion inside the turbinecasing, valve housings and condensers may exist as soon as the relativeair moisture of the ambient air inside the respective components exceedsa limit value or the surface temperature of the metal parts inside theturbine and valve housings and also condensers cools down in such a waythat the metal parts can fall below the dew point temperature.

In particular, the final stages of low-pressure turbine sections and thecondenser are at risk of corrosion since even during operation theirtemperatures lie close to the dew point or already lie below it.

In order to be able to put the steam power plant quickly into operationagain and in order to minimize the operating costs, the condensate inthe hotwell in the condenser is not released and remains inside thecondenser. This, however, results in the evaporation leading to anincrease of the moisture in the condenser and in the low-pressureturbine section adjoining it.

In order to avoid corrosion, provision is made for installing dry-airequipment after the first day of the shutdown. As a result of theoperation using dry-air equipment, dried air from the environment iscontinuously introduced into the turbine casing and therefore the entryof moist ambient air from the turbine hall is prevented. The introduceddry air absorbs moisture from the inside of the turbine casing and valvehousings and also from the condensers and is discharged again at definedopenings.

SUMMARY OF INVENTION

The invention has set itself an object of specifying another way ofeffectively preventing corrosion in the steam turbine after a shutdown.

This object is achieved by means of a method for operating a condenseras claimed.

The evaporation of the condensate is directly dependent on the size ofthe contact area between water and air. With the invention, the size ofthe contact area is effectively reduced by floating bodies beingarranged on the condensate. The contact area is reduced as a result ofthe floating bodies. Consequently, the evaporation in the hotwell isalso reduced. A lower moisture content is achieved and the risk of localmoisture points is especially reduced.

Furthermore, a lower volumetric flow of dry air is required, which leadsto a lowering of operating costs during the drying. By means of theinvention, the drying of the turbine is therefore effectively supported.

The floating bodies are arranged according to the invention in asufficiently large number in a floating manner on the condensatesurface.

Advantageous developments are disclosed in the dependent claims.

The floating bodies are advantageously of spherical and/or sphere-likedesign. In this case, shapes such as a strict spherical shape canfeature, i.e. the floating body is a sphere with a determined radius. Asopposed to this spherical shape, the floating body can also be ofsphere-like design, e.g. ellipsoidal.

The floating bodies advantageously have different sizes. Therefore, thecondensate surface can be still further effectively reduced since thepoints between the large floating bodies can be closed off by smallerfloating bodies.

Furthermore, in an advantageous embodiment the floating bodies aredesigned and arranged in such a way that the floating bodies havedifferent shapes. So, in addition to a spherical floating body,sphere-like floating bodies can therefore also be arranged next to eachother on the condensate surface. As a result, the condensate surface islikewise effectively reduced.

In a further advantageous development, the floating bodies are designedin such a way that rotation of the floating body is prevented. Due tothe impeded rotation of the floating body, it is possible that the samesurface always points to the condensate surface and the non-wettedsurface points opposite to the condensate surface. As a result, thenon-wetted surface remains dry. An increase of the air humidity isprevented as a consequence.

In an advantageous development, the floating bodies have differentdensities. This leads to the floating bodies being able to be arrangedin different layers on the condensate surface. The floating bodies in anadvantageous development are provided with a material surface which isas hydrophobic as possible. A hydrophobic surface results in anon-wettable surface. Therefore, the moisture is retained in thecondensate.

A further advantage of the invention is that existing condenser plantscan be retrofitted without restriction in a very simple and inexpensivemanner according to the invention. Since an adaptation to the specificcondenser geometry is carried out exclusively via the quantity offloating bodies, the invention can be put into operation inexpensively.No individual installed parts are necessary.

The floating bodies can be secured by measures such as aninterconnection or covering against undesirable suction by pumps.

Using the invention, the advantage of attaining a reduced evaporation inthe hotwell is therefore achieved. This means that a smaller quantity ofmoisture is created, as a result of which the air quantity which isrequired for the drying is reduced in turn. This benefits the dryingespecially in the region of the low-pressure turbine section and in theregion of the final stages. As a result, the cost of drying is lower andregions with increased moisture because of evaporation of the condensateare minimized. Furthermore, the risk of corrosion and the subsequentdamage to the turbine which is associated therewith is reduced.

Furthermore, by using a large number of floating bodies no individualadaptation to the shape of the condenser is required. The floatingbodies are automatically adapted to the current condenser geometry.Consequently, retrofitting of existing plants is possible in a simplemanner.

The characteristics, features and advantages of this invention which aredescribed above, and also the way in which these are achieved, becomemore clearly and more plainly comprehensible in conjunction with thefollowing description of the exemplary embodiments which are explainedin more detail in conjunction with the drawings.

Exemplary embodiments of the invention are described below withreference to the drawings. This drawing is not intended to definitivelyrepresent the exemplary embodiments, but rather the drawing, whereuseful for explanation, is embodied in schematized and/or slightlydistorted form. With regard to supplements to the teachings which aredirectly recognizable in the drawing, reference is made to theapplicable prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing:

FIG. 1 shows a cross-sectional view of a condenser,

FIG. 2 shows a cross-sectional view of a first embodiment according tothe invention of the floating bodies,

FIG. 3 shows a further embodiment of the floating bodies according tothe invention.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a cross-sectional view of a condenser 1 for a steam powerplant, which is not shown in more detail. The condenser 1 comprises aplurality of tube bundles 2 which are arranged in a steam flow 3. Cooledwater flows through the tube bundles 2, which leads to the water vaporfrom the steam flow 3 condensing on the surfaces of the tube bundles 2and, as water, coming into a region 4 in which the water collects toform a condensate 5. The steam flow 3 is fluidically connected to alow-pressure turbine section. Furthermore, the condenser 1 comprises aircoolers 6 which are arranged in the region of the tube bundles 2.

The condensate 5 forms a condensate surface 7.

According to the invention, floating bodies 8 are arranged on thiscondensate surface 7. In FIG. 1, for reasons of clarity, only threefloating bodies 8 are provided with the designation 8. These floatingbodies 8 wet the condensate surface 7 and consequently reduce thecontact area of the condensate surface 7 with the environment. Thefloating bodies 8 are of spherical and/or sphere-like design.Optionally, other shapes are also possible, as is the simultaneous useof different shapes and sizes.

Shown in FIG. 2 by way of example is an arrangement in which thefloating bodies 8 are arranged one above the other in a plurality ofrows, wherein the floating bodies 8 have different sizes and are ofspherical design in a first approximation.

FIG. 3 shows a further embodiment of the invention. The floating bodies8 are of sphere-like design in FIG. 3 and are also arranged one abovethe other in layers. Similarly, the floating bodies 8 are designed withdifferent sizes.

A further embodiment of the floating bodies 8 lies in the fact thatthese are of unsymmetrical design, which prevents rotation. As a result,the surface can dry more quickly.

The specific gravity of the floating bodies 8 is different and can beselected so that the steam flow cannot lift these out of the condensate.The floating bodies 8 can also have different weights so that, forexample, a better covering of the condensate surface 7 is achieved. Bythe same token, a different density is suitable for this purpose.

The number of floating bodies 8 is selected to be of sufficient size inorder to cover the surface of the condensate in the hotwell 9. Thenumber of floating bodies 8, however, can also be significantly greaterin order to therefore form a second layer of floating bodies 8, forexample.

The floating bodies 8 are preferably equipped with non-absorbentsurfaces so that in the ideal case no wetting of the surfaces takesplace.

Although the invention has been fully illustrated and described indetail by means of the preferred exemplary embodiment, the invention isnot then limited by the disclosed examples and other variations can bederived by the person skilled in the art without departing from thescope of protection of the patent.

1.-8. (canceled)
 9. A method for operating a condenser, wherein thecondenser is designed for condensing water vapor to form water andduring operation a condensate consisting of water accumulates in thecondenser, the method comprising: arranging on the condensate surface aplurality of floating bodies on the condensate, wherein the floatingbodies float on the condensate, wherein a large number of floatingbodies are used such that the condensate surface is covered, wherein thefloating bodies are of spherical and/or sphere-like design, and whereinfloating bodies with different sizes are used.
 10. The method as claimedin claim 9, wherein floating bodies with different shapes are used. 11.The method as claimed in claim 9, wherein a large number of floatingbodies are arranged in the condenser such that they lie one above theother.
 12. The method as claimed in claim 9, wherein floating bodieswith different densities are used.
 13. Floating bodies for floating on acondensate in a condenser, comprising: floating bodies designed for themethod as claimed in claim 9.